Jupiter’s most defining feature is arguably its Great Red Spot, a massive, swirling storm that astronomers have observed since the 1600s. In the 19th century, however, astronomers noticed the spot shrinking, and earlier this year shocking images led some scientists to suggest the massive storm was dying. But new modeling shows the storm is still raging and will likely continue to do so for the foreseeable future.
The Great Red Spot may have been originally discovered in 1664 by English scientist Robert Hooke, reports Kenneth Chang at the New York Times. Astronomers continued to see the oval until 1713, though it wasn’t recorded again for a century. It’s not clear if the spot disappeared and reformed, if a different spot formed, or if scientists simply couldn't find it for a time. In any case, the current rusty-red storm has persisted for at least 189 years and has been closely monitored ever since.
Jacob Stern at the Atlantic reports that since the late 1800s, astronomers have noticed the spot, an anticyclone storm about three times wider than Earth locked into place by opposing jet streams, has been shrinking. In 2012, skygazers noticed the shrinkage had accelerated. Earlier this year, amateur astronomers found that the normally oval-shaped spot looked a little deformed. Later, some observed that bits seemed to be “flaking” off of it. In May, some space enthusiasts began to suspect that the red spot could be unraveling. The spot eventually stabilized, but the incident has raised questions about the future of the iconic storm on Jupiter.
A new study by researchers at the University of California, Berkeley, and presented at a conference of the American Physical Society's Division of Fluid Dynamics, however, reports that the underlying vortex powering the spot is unchanged. Berkeley fluid dynamicist Philip Marcus and his team analyzed high-resolution images of the Great Red Spot and compared them to another big storm on Jupiter. They found that what goes on in the upper layer of clouds that optical telescopes can see isn’t a good measure of the vortex powering the storm itself, which may be more than 200 miles deep in the clouds of Jupiter.
“I don’t think [the Great Red Spot’s] fortunes were ever bad,” he says in a press release. “It’s more like Mark Twain’s comment: The reports about its death have been greatly exaggerated.”
Marcus explains that the red spot's “flakes,” “blades,” and “hooks” seen earlier this year are normal occurrences for a vortex covered in clouds, and they don’t indicate the physical processes powering the storm are breaking up.
“You can’t just conclude that if a cloud is getting smaller that the underlying vortex is getting smaller,” he tells Chang.
Marcus’s simulations show that the bits amateur astronomers saw peeling off the Great Red Spot were probably pieces of another smaller storm. Perhaps a small cyclone—one that spins in the opposite direction of the giant anticyclone—collided with the big storm, creating a point of stagnation, with the winds of the two opposing storms deflecting each other like “two fire hoses aimed at one another,” Marcus tells Chang.
At the same time, the Great Red Spot seems to have gobbled up a smaller anticyclone and merged to form a bigger storm. As the little anticyclone was spun around in the red spot, it collided with the stagnation point, which sliced off the blade-shaped clouds seen by observers. Ashley Strickland at CNN reports that Marcus suspects the “flakes” breaking off the GRS were actually “undigested” pieces of the smaller anticyclone.
Those encounters with smaller storms have little impact on the underlying stability of the red spot’s vortex, which is powered by cycles of heating and cooling that occur above and below it that have kept it spinning for centuries. It will probably keep on brewing for centuries to come, reports Samantha Mathewson at Space.com.
“Unless something somewhat cataclysmic happens on Jupiter, it will last for the indefinite future, until the jet streams change, so I would say likely centuries,” Marcus said at a news conference. “Of course, I probably just gave it the kiss of death, and it’ll probably fall apart next week, but that’s the way science works.”
Other researchers have also concluded that the images of bits flaking off the cyclone are not evidence the spot is dying. Amy Simon, who leads NASA’s Outer Planets Atmospheres Legacy program, tells the Atlantic that visually, it appeared the red spot was shedding gas, especially because the anticyclone it consumed was the same color. But when her team looked at the velocity of the storm instead of the colors, it showed the gas was flowing into the spot, not out.
“It’s always doing this,” Simon says. “[The Great Red Spot] is always pulling stuff in and parts of it are flying off. That is not unusual at all.”